Generally, in case that the operation of a switched reluctance motor (SR motor) without a permanent magnet is switched from driving to braking, regeneration of energy is performed by switching to so-called “operation mode of the generator” for converting the braking energy into electrical energy.
On the regeneration, a complicated regeneration circuit is used for necessity of returning a voltage generated with maintaining an exciting current of the SR motor to source-side. Also, a complicated circuit using a reactor and a capacitor etc. is used on the foregoing energy conversion.
Here, in the following patent document 1 and 2, regeneration-type SR motor driving systems are disclosed for downsizing the SR motor and for improving the energy recovery efficiency on the regenerative braking etc.
And, in the paragraphs [0044] etc. of the following patent document 3, a technique is disclosed for returning to the direct-current source 30 the current flowing through the winding for driving the SR motor.
And, in the paragraphs [0045] to [0056] of the following patent document 4, a technique is disclosed for reduction of the current consumption in the battery B by the energization control using the source of the battery B only in a predetermined time from starting the control of the SR motor 10 and using the energy stored in the first-phase coil CL1 for the rest of the time.
Here, in the technique, as seen in the paragraphs [0050] to [0051] of the patent document 4, the current I is gradually increased toward the target current value again by judging the timing of turning on the first low-potential-side transistor QL1 based on a timer so as to reestablish the closed-loop after the current I flowing through the first-phase coil CL1 has been reduced from the target current value.